The need to communicate is an endemic need of modern society. Data must be communicated, sometimes between very widely spaced apart locations, to effectuate many varied communication services. Communication systems are used to effectuate the communication of the data. A communication system is formed, at minimum, of a sending station and receiving station interconnected by way of a communication channel. Many different types of communication systems have been developed and deployed through which to effectuate many different types of communication services.
As technological advancement warrants, new types of communication systems have been developed and deployed. Technological advancements continue and communication systems that embody such advancements continue to be deployed.
Many modern communication systems utilize digital communication techniques. Digital communication techniques provide several inherent advantages over analog communication techniques. Perhaps most significantly, increased communication efficiency is possible through the use of digital communication techniques. And, as result, the communication capacity of a communication system that utilizes digital communication technique is generally significantly greater than the communication capacity available to a corresponding communication system that utilizes analog communication techniques.
A radio communication system is a type of communication system in which the communication channels interconnecting the communication stations thereof form radio channels, defined upon a radio air interface extending there between. The infrastructure required to implement a radio communication system is generally less than that required of a corresponding wireline counter part. And, the cost required to deploy the infrastructure of the radio communication system is generally less than the corresponding cost to deploy the wireline counterpart. Additionally, a radio communication system is amenable for implementation as a mobile communication system in which mobility of communication is provided.
A cellular communication system is a type of radio communication system. The network infrastructures of cellular communication systems have been deployed over significant portions of the populated areas of the world. Successive generations of cellular communication systems have been developed and deployed. And, successor generation systems are undergoing deployment or standardization.
Other wireless networks have also been deployed, sometimes incorporating various aspects of cellular communication systems. For instance, wireless local area networks (WLANs) as well as wider-area, wide area networks (WANs) are increasingly being used to communicate data, both voice data and non-voice data. An IEEE (Institute of Electrical and Electronic Engineers) 802.11 standard, and variants thereof, defines operating parameters by which many wireless LANs are operable. WLANs are implemented at both licensed and non-licensed bands of the electromagnetic spectrum. When a user has a choice of communicating by way of a commercial, cellular communication system and a private WLAN, use of a private WLAN is sometimes preferred for the reason that communication costs associated with the private network are generally less than corresponding costs to communicate by way of a commercial cellular communication system.
Some wireless local area networks provide for communication hand offs to permit continuation of communications with a mobile node as the mobile node travels throughout an area encompassed by a plurality of fixed site radio transceivers, sometimes referred to as access points (APs). Sometimes brief service interruptions occur when the communications are handed off from a serving access point to a target access point. That is to say, the serving access point is disassociated with the communications, and the target access point becomes associated with the communications. When the communication of the data is not time sensitive, the brief service interruption is usually insignificant. However, when the communication of the data is time sensitive, such as when the communication service forms a telephonic voice communication, the interruption is noticeable and potentially reduces the quality of service (QoS) of the communication session.
As an example, the service interruption, i.e., the period of time during which a channel is unavailable to communicate the data, might be as long as 300 ms. If the packets of the data communication are of lengths such that the packets are communicated once every 20 ms, then, for a 300 ms interruption, approximately 15 real time packets are delayed or dropped during the handoff of communication. As the communication range of an access point might be 30 meters, or less, multiple handoffs between successive access points might be required during a single communication session. Repeated service interruptions, and their noticeable effects might well have a compounding effect on a user perception of the quality of the communications as well as a quantitative QoS level.
A manner by which to preserve the quality of service level of communications during hand-off of the communications between source and target access points, or other entities, would therefore be beneficial.
It is in light of this background information related to communication handoff procedures that the significant improvements of the present invention have evolved.